Interesting that you don't mention Niasse !
Keane is going through a rough time, but I can see him coming through and being a key part of our defensive setup for the next 5 years, and I'm sure others would agree, so I reckon his price today would be much the same.
With the other names on your list, the issue isn't really how much we overpaid for them (probably a bit less than you think, and in the case of Bolasie we're only just starting to find out how much he has to offer after his 12 month lay-off), but whether we targeted the right players. It's debateable firstly whether any of them have the quality we need to build a team that can break into the top 4, and secondly how far they fit into how we want to set up the team and what style of football we want to play. This is the big worry : that we're bringing in players who can't improve us. But I wouldn't write this lot off yet.